Mobile process monitor system for kilns

ABSTRACT

An industrial mobile process monitoring system is described which provides a way by which a measurable atmospheric condition, such as temperature, can be measured in real time at a plurality of different locations in a structure such as a kiln, and the information transmitted to a base station computer via magnetic energy linking primary and secondary windings of an air-core transformer.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates generally to a system for monitoring thetemperature within a kiln, and more particularly, to a system formeasuring the temperature at a plurality of different locations onmoving kiln cars.

Kilns have long been used in the manufacturing of ceramic articles. Justa few examples of the many articles (ware) that are made with the use ofkilns are tiles, bricks, refractories, china, earthenware, electricalporcelain items, spark plugs, toilets, and bathroom sinks just to name afew. Products such as these are placed in a kiln to be baked or fired bytemperatures far in excess of 1,000 degrees centigrade. Kilns in usetoday around the world come in various shapes and sizes to serveproduction needs of particular articles. For example, tunnel kilns canbe in excess of 100 feet long having a track running through them forconveying multiple cars of articles to be fired in a mass productionenvironment, while shuttle kilns have cars full of articles to be fired,moved into the kiln one at a time.

It is desirable to be able to monitor atmospheric conditions, such astemperature, carbon monoxide levels, oxygen levels, C02 levels, humidityor water vapor levels, and sulphur oxide levels, inside of a kiln, atdifferent locations or zones within the kiln, in order to optimize thefiring process. High temperature thermocouples acting as temperaturetransducers may be used. Specifically, it is desirable to monitor thetemperature in and around the articles or objects being fired.

In a tunnel kiln the objects being fired are in continuous motion thoughthe kiln making it difficult to monitor the temperature in and aroundthe moving objects. A plurality of cars carrying the articles to befired, move on tracks through the kiln. Because the articles to be firedare resting on top of the cars, and since it is the object of the kilnfiring process to fire the articles, it is not essential to heat thezone of the kiln in the vicinity under the cars. Therefore, this area ismaintained at a much lower temperature than the firing regions above thecar beds or decks. The underside of the cars are also somewhat insulatedfrom the heat existing above the car beds due to the fact that the carsare often in end-to-end contact and heat seals may be placed on thesides of the deck of each car in close relation to the walls of thetunnel kiln. This can greatly reduce the underside temperature. However,the temperature under the cars can still reach a level up to 200 degreesCelsius.

It is known to use thermocouples to transmit temperature data to theexterior of a kiln. Some approaches have used either a data logger or atelemetry device to transmit the temperature data. A disadvantage ofusing a data logger is that the temperature data is not available untilafter the car exits the kiln. This precludes real time analysis andadjustment of the temperature within the kiln. Telemetry units alsosuffer from disadvantages. One is the fact that many tunnel kilns aremade of steel which is not especially conducive to radio transmissions.Industrial radio telemetry links usually tend to be quite expensive.Additionally, because kilns are used in a variety of countries aradio-based telemetry link may face governmental regulation on thefrequencies that could be emitted. A need exists for a real timetemperature monitoring system for measuring, transmitting, and receivingtemperature data from a variety of locations within a kiln.

The present invention may be applied to measure temperature andtemperature distribution within a setting of articles being fired in atunnel kiln or a shuttle kiln. The temperature data received will allowvariation of operating processes by an operator of a kiln to reduceundesired gradients or otherwise to correct for temperatures which areeither above or below the desired firing schedule. Two commonly usedfiring procedures are generally known as "continuous" and "periodic".Tunnel kilns and shuttle kilns, respectively, are associated with thesefiring procedures.

Tunnel kilns typically have a railed track much like a railway system.Cars which will carry the articles to be fired move on wheels over thesetracks. A temperature profile is maintained in the space above the decksof the cars such that the entrance end and the exit end of the tunnelare at a much lower temperature than the center of the length of thetunnel. The cars generally move rather slowly through the kiln so thatthe articles atop each car experience a gradual rise in temperature to amaximum level which is subsequently lowered as the articles near theexit of the kiln.

Periodic firing was the more common method of kiln usage in the past.Under the periodic method the kiln is filled with ware, fired to itsmaximum temperature, cooled, and then unloaded. The drawback with thisprocess is that major energy losses accompany it as compared to thermalefficiencies which are achieved under continuous firing. Severaladvantages do exist however, for periodic firing. These include theflexibility in production scheduling, variation in size and shape of theware which may be accommodated, atmospheric and temperature controlbeing more manageable, and improved thermal design efficiencies. Moremodern methods of periodic firing make use of shuttle cars to rapidlyremove one or more cars from a kiln and place another car(s) to be firedinto the kiln.

Thermocouples used to monitor the temperature at various locationswithin a kiln must be situated so as not to interfere with the passageof articles in the tunnel kiln, or with the insertion/removal ofarticles from a shuttle kiln. It would be advantageous to havetemperature measurement throughout the setting of the articles beingfired, such as at a point deep within a stack of ware, near theinsulating deck of a car, close to the top of the setting of the warebetween articles, and from side to side of the setting. The presentinvention is designed to accomplish such detection while the articlesbeing fired go through the thermal process within the kiln.

Modern firing technology within a kiln is directed to the goal ofoptimum use of energy to achieve the desired fired properties for thearticles. Detailed familiarity with the chemical and physical behaviorof the ceramic material being processed is very beneficial to computingthe optimum use of energy. Most ceramics undergo complex chemicalreactions commensurate with their composition, thermal and gaseousexposure time. Heating often causes the decomposition or oxidation ofmineral constituents with the evolution of gases and/or significantchanges in physical size and bonding strength. Chemical reactionsstimulated by intimate contact of the reactant particles at hightemperatures generally create new compositions, some of which becomeliquid. The densification and strength development is usuallyaccompanied by shrinkage and a reduction in the ability of the materialto transport gases to and from the reaction sites within the ware.Temperature gradients imposed by the difficulties of heat penetrationthroughout the ware setting can result in variations in the firedproperties of ware from different locations within the setting. Evenworse, there may be bloated, cracked or warped ware as a result of suchgradients, or strains which show up only in later service as spontaneouscracking.

The cooling phase can be disastrous to fired ware, since the material isnow rigid and generally behaves in a brittle fashion. Thermal gradientsaccompany the cooling process, so there are thermal strains generatedwithin the ware due to differential shrinkages. Some mineralconstituents undergo rapid phase changes over narrow temperatureregions, often associated with relatively large change of physical size.If such materials are subjected to temperature changes which are toorapid, they will generate major failure cracks during the cooling.

The above considerations lead to the design of firing and coolingcurves, including "soak" times at constant temperature, which willresult in the maximum production of first quality finished articles inthe minimum time with the least amount of fuel for the firing process.To help attain these goals a detailed knowledge of temperaturevariations throughout the ware setting may be obtained so thatprocessing techniques may be introduced to minimize such variations andtheir effects. Many modern burner systems utilize pulse firing and/orhigh velocity hot gases directed to the elimination of gradients.Variations in patterns of ware setting may be developed to alleviatesome of these problems. Limits on the rate of heating are oftenestablished on the basis of unavoidable gradients. Whatever method isused, it is required that temperature measurements or other means ofdetection of thermal gradients be utilized to best accomplish thesegoals. With temperature data available during the firing process it ispossible to directly observe influences of adjustment which are made.The present invention offers a system by which this result is achieved.

The present invention comprises non-contacting transmission of data froma remote location, such as under a kiln car, to a base station which maybe located at any convenient site within a factory, via a magneticcoupling which may operate with negligible radiative output. The presentinvention comprises a plurality of thermocouples, signal conditioningelectronics, a phase-change type thermal enclosure, a telemetry linkusing a nonradiating magnetic coupling, and a data display/recordingdevice located external to the kiln.

The car mounted electronics package of the present invention includesthermocouple signal conditioning electronics. The resulting signals areconverted into digital form and are read by a microcontroller. Themicrocontroller communicates with the base station via a specialtelemetry link. The base station is the other end of the telemetry linkwhich may include a personal computer. Software on the base stationcomputer may provide for the display and storage of the temperaturedata. The base station may be capable of communicating with many cars ona time-multiplexed basis.

The connection from the microcontroller to the base station computer maybe an RS-232 format serial communications link preferably capable ofoperating at around 300 baud or greater. Each end of the telemetry linkmay contain both a transmitter and a receiver.

The transmitter and receiver are linked by an air core signaltransformer of the present invention comprised of loops of wire whichare arranged in such a way as to obtain good magnetic coupling betweenthe base station and the mobile sensor unit(s). In a tunnel kilnapplication, the signal transformer winding may comprise several turnsof wire wrapped around the perimeter of the car. The base station signaltransformer winding (STW) may comprise a wire which is routed in astraight path through the tunnel kiln near one of the tracks, returningin a straight path near the other track. The transmitter may comprise asquare wave oscillator which transmits when the RS 232 input signal isat logic one, and is idle when the input is at logic zero. The receivermay comprise a preamplifier and an AM demodulator circuit. A pluralityof cars may use the same frequency under a software handshakingprotocol, with the base station acting as the master. The telemetry linkis that of an air-core transformer.

Other objects and advantages of the present invention will become moreapparent upon consideration of the following detailed specification anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an entrance to a tunnel kiln with aloaded car about to enter the kiln;

FIG. 2 is a schematic block diagram of the overall system of the presentinvention;

FIG. 3 is a schematic block diagram of a mobile sensor unit of theprevent invention;

FIG. 4 is a schematic block diagram of a modulator/transmitter of thepresent invention;

FIG. 5 is a schematic block diagram of a receiver/demodulator of thepresent invention;

FIG. 6 is a schematic block diagram of a personal computer communicationboard for use with the present invention;

FIG. 7 is a schematic representation of an air-core transformer of thepresent invention; and

FIGS. 8 A-R are electrical circuit diagrams of components of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENT(S)

Referring now to FIG. 1, there is shown a tunnel kiln 20 entrance 22 forreceiving a car 24 movable on a track 26. The car 24 is loaded witharticles 28 to be fired in the kiln 20. The articles 28 rest on the deck30 of the car 24. The railroad-like tracks 26 pass longitudinallythrough the tunnel of the kiln. The interior of the tunnel of the kilnis adapted to generate very high levels of heat to fire or bake thearticles that pass through the kiln.

Referring to FIG. 2, the present invention comprises three majorsubsystems: a base station computer 32; mobile sensor units 34; and anair-core signal transformer 36 used as the communication link betweenthe base station 32 and the mobile sensor units (MSU's) 34. The presentinvention provides a means by which the temperature at a plurality ofdifferent points on each of a plurality of moving kiln cars, can bemeasured, transmitted to a fixed computer, may be displayed graphically,and the data stored for later analysis. Provision may also be made todetect when each kiln car moves past a certain location.

The air-core signal transformer inputs include a primary winding 38connected to the base station computer and secondary windings 40connected to the MSU's. The air-core signal transformer outputs includea primary winding connected to a base station computer and secondarywindings connected to the MSU's. Communication between the computer andthe MSU's is established via magnetic energy linking primary andsecondary windings of the air-core signal transformer. The transformermay be designed to operate efficiently at a selected excitationfrequency, such as 20 kHz. Since the physical dimensions of thetransformer windings are negligibly small relative to the wave length ofthe excitation source, negligible electromagnetic radiation is produced.

Referring particularly to the transformer primary winding it may have asits inputs an on-off modulated electrical excitation from the basestation computer and magnetic flux from the secondary windings. Theoutputs may include an on-off modulated voltage to the base stationcomputer and magnetic flux to the secondary windings. The primarywinding in a preferred embodiment of the present invention consists of asingle turn loop of wire. The loop is formed by running a conductorthrough the kiln beneath the kiln cars, but above the floor of the kilnand parallel to the tracks inside the kiln. Preferably the wire runsparallel to one side 42 of the track until it reaches an end of thekiln-and there it forms a loop to the other side 44 of the tracks andfollows the other track rail, running parallel to it, back through thekiln on the opposite side of the first pass of the wire. The resultingloop of wire 38 is preferably oriented horizontally. The wire may besupported by a variety of different support means such as insulatorposts 46 secured to the floor.

The secondary windings of the transformer have as inputs an on-offmodulated electric excitation from individual MSU's, and magnetic fluxfrom the primary winding. The outputs of the secondary windings includethe on-off modulated voltage to individual MSU's, and magnetic flux tothe primary winding. Preferably one multiple-turn secondary winding 40is installed around the bottom periphery 41 of each of the MSU-equippedcars. This winding preferably has the same horizontal orientation as theprimary winding.

Referring to FIG. 7, the transformer coil geometry for a given kiln maypreferably incorporate the following relationships:

B is less than or equal to E/10;

A is greater than or equal to B/2;

C is greater than or equal to B/2;

the absolute value of D is less than or equal to B; and

the absolute value of F is greater than or equal to B/2.

The electronics assembly mounted on the cars in one embodiment does notcontain provisions for matching the impedance of the secondary coils.Thus the number of turns of each secondary coil is chosen to make theinductance of the coil approximately one millihenry. The inductance of around air-core coil with a diameter very much greater than its length isapproximately determined by the equation:

    L=3.585* N.sup.2 * D MICROHENRIES

In the equation N is the number of turns and D is the diameter of thecoil in meters. The inductance of a rectangular loop can be approximatedfrom this equation, thus given the loop diameter and the specifiedinductance, the appropriate number of turns N can be computed.

The base-station computer has as its physical input the air-coretransformer primary winding, and as its data input, the messagestransmitted thereon. The output of the base station computer includesthe graphical and numerical temperature data in human readable form,temperature data files, and its physical output is the air-coretransformer primary winding. The base-station computer may be programmedto graphically display temperature data in real time, and store data forlater analysis.

The temperature data is obtained from each of the MSU's. Thebase-station computer communicates with the MSU's preferably using aserial data protocol over the air-core signal transformer. Thebase-station may act as a moderator, commanding each of the MSU's totransmit only when specifically requested by the base-station. Thiswould result in no more than one winding of the air-core transformerbeing driven at any given instant.

The base-station computer preferably comprises an industry standardarchitecture (ISA) personal computer (PC), application software toimplement the functionality described above, and a PC communicationboard. The inputs to the PC communication board may include on-offmodulated serial data from the air-core transformer and the ISA bus dataand control. The outputs from the communication board would includeon-off modulated serial data to the air-core transformer and ISA busdata and control. The communication board provides the base-station PCwith the ability to communicate over the air-core signal transformer tothe MSU's.

As shown in FIG. 6, the communication board preferably comprises fivefunctional blocks of circuitry: a standard bus interface circuit 50; anRS 232 UART standard circuit 52; a modulator/transmitter 54; ademodulator/receiver 56; and an impedance-matching transformer 58 whichmay be used to step-down the drive voltage from the base stationtransmitter prior to being applied to the primary coil. Without thistransformer the primary coil current would be excessively high due toits low inductance.

As shown in FIG. 3, each mobile sensor unit of the present inventionpreferably has several inputs from a plurality of thermocouple 48connections, a kiln car home position switch 80, and the air-coretransformer secondary winding 40. The output of each mobile sensor unitwould preferably be the air-core transformer secondary winding. TheMSU's are attached to the underside of the kiln cars, preferably intemperature regulated enclosures. The MSU's preferably contain thecircuitry necessary to amplify the thermocouple signals 48, convert themto digital format, and transmit the digital information to thebase-station computer upon command. In one preferred embodiment of thepresent invention each MSU comprises up to fourteen functional blocks ofcircuitry which are described hereinafter.

Each MSU would preferably have a precision voltage reference 82 (alsoshown in FIG. 8A). This is a highly stable circuit which produces aprecise DC voltage under all conditions. The absolute accuracy of theprecision reference voltage determines the accuracy of the overallsystem. All other significant sources of error may be removed throughself-calibration procedures.

Each MSU would preferably contain a low level voltage reference circuit84 (also shown in FIG. 8B). This circuit reduces the precision referencevoltage to a value which is comparable to thermocouple output voltages.It can be input to the instrumentation amplifier circuitry and used tocalibrate the amplifier and analog-to-digital converter.

Each MSU would preferably have an ice-point/zero-voltage reference 86(also shown in FIG. 8C). This circuit serves two functions. First, itpreferably contains a precise electronic thermometer which is used tomeasure the temperature inside the electronics enclosure. Thisinformation is used to compute absolute thermocouple temperature. Thebasic thermocouple circuitry may only measure the thermocoupletemperatures relative to the temperature inside the electronicsenclosure. The second function of this block of circuitry is thecapability to command the electronic thermometer to turn off its outputwhich results in zero volts being output. This voltage can be input tothe instrumentation amplifier and used to calibrate the instrumentationamplifier and the analog-to-digital converter.

Each MSU would preferably include a low level analog multiplexer 88(also shown in FIG. 8D). The circuit of the multiplexer would preferablybe of conventional design and used to connect any one of the low levelvoltage inputs (from the thermocouples, the low level voltage reference,and the ice point/zero voltage reference) to the instrumentationamplifier. The multiplexer may be a differential type constructed ofreed relays. An alternative design is to provide separate amplifiers foreach signal, then use a high level, solid state analog multiplexer.Inputs of this block of circuitry are connected to the instrumentationamplifier as commanded by the microcontroller.

Each MSU may further include a thermocouple fault detection means whichallows the MSU to automatically detect any disconnected or brokenthermocouples. A low level voltage reference circuit may be connected inparallel with each thermocouple input. When a voltage is applied to thecircuit, if a thermocouple is broken, the resulting voltage will beequal to the low level voltage reference.

Each MSU preferably includes an instrumentation amplifier 90 (also shownin FIG. 8E). This circuit may be of conventional design, to amplifysmall voltages (such as those generated by thermocouples) to a levelwhich is compatible with the analog-to-digital converter input. It ispreferably a differential type amplifier, which means that potentialerror sources (such as electromagnetic radiation) which cause equalerror voltages to appear on both thermocouple leads will not causemeasurement errors.

Each MSU preferably includes a battery monitor circuit 92 (also shown inFIG. 8F). The circuit converts voltages from the two power supplybatteries to levels which are compatible with the analog-to-digitalconverter. This allows the microcontroller to monitor the batteryvoltages and issue warnings before the batteries become fullydischarged.

Each MSU preferably includes a high level analog multiplexer 94 (alsoshown in FIG. 8G). This circuit is preferably of conventional design andallows the microcontroller to select any of three high level voltages(the instrumentation amplifier output and the two battery voltages) forconnection to the analog-to-digital converter.

Each MSU preferably contains an analog-to-digital converter circuit 96(also shown in FIG. 8H) of conventional design. This circuit convertsanalog voltage levels to binary digital values. Preferably theparticular converter used provides self-calibration features and aserial data interface to the microcontroller 98 (also shown in FIG. 8I).

Each MSU preferably includes a microcontroller 98 of a standardconfiguration known to those of ordinary skill in the art which providesall of the functionality of a small computer. It may also have manydigital I/O lines to control other circuitry and provide an RS 232format input and output for communication with the base-stationcomputer. Software installed in the microcontroller may provide for dataprocessing, communication, and control features needed on each MSU.

Each MSU preferably has unit ID switches 100 (also shown in FIG. 8J).This circuit may contain seven switches connected to the microcontrollerwhich are used to uniquely identify each of the MSU's which may beincorporated in a given kiln monitor system. The unit ID would allow thebase-station to address each MSU individually.

Each MSU would preferably include a home position switch input 80 (alsoshown in FIG. 8H). This provision is made for the connection of anormally open switch to a microcontroller input. For example, thisswitch would be closed upon reaching a certain location such as the kilnentrance. This would allow the base-station to establish the position ofeach MSU that is in service.

Referring to FIG. 4, each MSU would preferably contain amodulator/transmitter circuit 59. The input to the circuit would be theTTL-level, RS 232-format serial data 52 while the output would be theon-off modulated, RS 232-format serial data 53 to the air-coretransformer winding or the impedance matching transformer. This circuitconverts the TTL-level, RS 232-format serial data into on-off(amplitude) modulated, RS 232-format serial data, and transmits theresulting signal over the air-core magnetic transformer. Since theserial data is binary, only two amplitudes are needed: on and off (zerovolts). The modulation frequency used is preferably approximately 20kHz. The modulator/transmitter preferably comprises three functionalblocks of circuitry. The first is a square wave oscillator 60 of astandard circuit (shown in FIG. 8L) which generates a square wavesuitable with a four quadrant power bridge. The second block ofcircuitry (shown in FIG. 8M) is the on-off modulator/bridge controller62. When the transmit input is true, this circuit generates controloutputs to the four quadrant power bridge 64 which cause it to output a20 kHz square wave. When the transmit signal is false, the power bridgeis set to a high impedance state. The third functional block ofcircuitry in the modulator/transmitter is a four quadrant power bridge64. This is a standard circuit (shown in FIG. 8N) generally used inpulse width modulated motor control circuits. It is preferred for thisapplication because of its excellent energy efficiency.

The final preferred functional block of circuitry in each MSU is areceiver/demodulator circuit 69 (shown in FIG. 5). This circuit may haveas its input on-off modulated RS 232-format serial data from theair-core transformer winding or the impedance matching transformer 58.Its output would be TTL-level, RS 232-format serial data 52. Thereceiver/demodulator converts RS 232-format, on-off modulated signalsfrom the air-core transformer (or impedance matching transformer) intoRS 232-format, TTn-level signals. It preferably comprises fourfunctional blocks of circuitry. The first is a transient protectioncircuitry 70 of conventional design (shown in FIG. 80) which preventsstatic discharges or other sources of high voltage from damaging thereceiver inputs. The second is a band pass filter 72 of conventionaldesign (shown in FIG. 8P) which permits the communication signals topass through, but blocks all other frequencies (which could otherwiseresult in interference problems). The third is an AM demodulator circuit74 of conventional design (shown in FIG. 8Q) which produces an outputvoltage that is proportional to the amplitude of the incoming signal.Fourth is an on/off threshold detector 76 of conventional design (shownin FIG. 8R) which detects if the amplitude of the incoming signal islarge enough to be considered "on". The output of this circuit is at avoltage level compatible with digital logic circuitry.

It should be noted that the foregoing disclosure describes onlypreferred embodiments of the present invention and that modificationsmay be made therein without departing from the spirit and scope of theinvention. For example, although thermocouples have been discussed inconnection with the preferred embodiment, it is possible to incorporateother sensors in a manner similar to that described herein forthermocouples. The system of monitoring temperature and controlling thetemperature profile of a kiln may have equal application to otherindustries. The various circuits described herein and shown in theaccompanying drawings are clearly susceptible to modification withoutdeparting from the overall function, means, and result of the presentinvention.

What is claimed is:
 1. A kiln monitor system, for a kiln comprising:amobile sensing unit which detects temperature data at various locationswithin a setting of articles being fired while on a moving carrier insaid kiln; a communication link employing magnetic coupling for sendingsignals characterizing said temperature data, to a conductor whichconveys said signals to a station outside of said kiln while saidsetting of articles are being fired; a communication circuit at saidstation outside of said kiln for receiving said temperature data signalsand for sending a command signal to said mobile sensor unit; and acomputer for processing said temperature data, and for generating ahuman readable output characterizing said temperature data signalssignals.
 2. The system of claim 1, wherein said mobile sensing unitincludes a receiver to receive temperature signals from at least onetemperature detecting device; a converter to change said temperaturedata signals to digital format; and a transmitter to convey saidtemperature data signals in said digital format to said computer.
 3. Thesystem of claim 2, wherein said at least one temperature detectingdevice is a thermocouple.
 4. The system of claim 1, wherein saidcommunication link includes an air-core signal transformer.
 5. Thesystem of claim 4, wherein said air-core signal transformer comprises aprimary winding connected to said communication link and in proximalassociation with said kiln, and a secondary winding connected to saidmobile sensing unit said primary winding and said secondary winding in aspatial relationship that allows for magnetic energy to link saidprimary and secondary windings to permit communication therebetween. 6.The system of claim 5, wherein said primary winding comprises a sinsingle turn loop of wire running substantially parallel to a set oftracks within said kiln on which said carrier is movable.
 7. The systemof claim 5, wherein said secondary winding comprises a multiple turnwinding of wire secured to the underside of said moving carrier.
 8. Amethod for monitoring the interior of a kiln during its operation, saidmethod comprising the steps of:providing a movable carrier on which toplace articles to be fired in said kiln; placing said articles on saidmovable carrier; providing at least one atmospheric condition sensorpositioned within or near a setting of said articles on said movablecarrier; causing said movable carrier to move within said kiln; causingsaid articles to be fired; sensing at least one atmospheric conditionwithin said setting of articles on said movable carrier as said settingof articles are fired; quantifying said at least one atmosphericcondition into transmittable signals; transmitting said transmittablesignals via magnetic coupling to a conductor which conveys saidtransmittable signals to a receiving location outside of said kiln; andprocessing said received transmittable signals to generate an outputthat characterizes said condition(s).
 9. The method of claim 8, whereinsaid transmitting is accomplished by an air core signal transformerarrangement.
 10. The method of claim 8, wherein said at least oneatmospheric condition include temperature.